Clock Tree Synthesis Using Force-Directed Algorithm

The patent performs preliminary actions by pre-calculating optimal branch positions using force-directed algorithms before actual clock tree synthesis. Graph models are constructed with weight values representing path lengths or timing characteristics, and guide buffers are positioned in advance at calculated optimal locations. This preliminary planning enables the clock tree synthesis process to achieve better timing balance and reduce on-chip variation while maintaining high integration density.

The patent applies parameter changes by dynamically adjusting weight values in the graph model based on timing analysis results. The force-directed algorithm uses these weight values to recalculate branch positions, and the process iterates with updated parameters until setup time constraints are satisfied. This iterative parameter adjustment optimizes the clock tree structure to minimize OCV while maintaining transistor integration density.

The patent implements feedback mechanisms through iterative post-CTS static timing analysis that feeds back into the synthesis process. After initial synthesis, timing analysis identifies violations, which trigger recalculation of weight values and repositioning of guide buffers. This feedback loop continues until timing constraints are met, ensuring reliable chip performance while managing synthesis complexity through automation.

The patent introduces guide buffers as intermediary elements between the clock source and clock pins. These guide buffers act as mediators that receive clock signals and distribute them to multiple branches, enabling better timing control and reducing the impact of timing variation. The guide buffers are positioned at optimal locations calculated by the force-directed algorithm to minimize path length differences and improve overall timing balance.